Executive summary - Diagnosis, treatment and prophylaxis of influenza virus infection - Consensus statement of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC), the Spanish Society of Pediatric Infectious Diseases (SEIP), the Spanish Association of Vaccinology (AEV), the Spanish Society of Family and Community Medicine (SEMFYC) and the Spanish Society of Preventive Medicine, Public Health and Health Management (SEMPSPGS).

The influenza virus has accompanied humans since time immemorial, in the form of annual epidemics and occasional pandemics. It is a respiratory infection with multiple repercussions on people's lives at an individual and social level, as well as representing a significant burden on the health system. This Consensus Document arises from the collaboration of various Spanish scientific societies involved in influenza virus infection. The conclusions drawn are based on the highest quality evidence available in the scientific literature and, failing that, on the opinion of the experts convened. The Consensus Document addresses the clinical, microbiological, therapeutic, and preventive aspects (with respect to the prevention of transmission and in relation to vaccination) of influenza, for both adult and pediatric populations. This Consensus Document aims to help facilitate the clinical, microbiological, and preventive approach to influenza virus infection and, consequently, to reduce its important consequences on the morbidity and mortality of the population.

[Evaluation of a community-based intervention to increase influenza vaccination coverage in pregnant women]. / Evaluación de una intervención comunitaria para incrementar la cobertura vacunal de la gripe en mujeres embarazadas.

OBJECTIVE: To know the impact of the educational intervention carried out on the professionals of a basic health area and their community participation group, which make up the intervention group (IG), and to analyze its repercussion on the vaccination coverage achieved for influenza in the risk group (pregnant and puerperal women) comparing it with its neighboring basic zone, which makes up the control group (CG), during the 2019/20 vaccination season. DESIGN: Quasi-experimental study of community intervention. SITE: Two basic health zones belonging to the Elche-Crevillente health department, Spain. PARTICIPANTS: Pregnant and postpartum women from 2 basic health areas and the community participation group. Health professionals directly related to the flu vaccination campaign. INTERVENTIONS: Training session for the IG prior to the 2019/20 flu campaign. MAIN MEASUREMENTS: Attitudes towards influenza vaccination in health professionals through the validated CAPSVA questionnaire and the vaccination coverage of pregnant and postpartum women through the Nominal Vaccine Registry and their acceptance of the vaccine in the midwife's office. RESULTS: The influenza vaccination coverage data recorded in Nominal Vaccine Registry for pregnant and puerperal women was 26.4% (n=207) in the IG and 19.7% (n=144) in the CG (p=0.001), with an incidence ratio of 1.34, thus achieving 34% more vaccination in the IG. Acceptance for vaccination in the midwife's office was also high, with 96.5% immunization in IG vs. 89.0% in CG, with a RR=1.09 (95% CI 1.01-1.62). CONCLUSIONS: Joint training strategies for professionals and community assets improve the results of vaccination coverage.

National retrospective cohort study to identify risk factors for in-hospital 30-day lethality in laboratory-confirmed cases of influenza. / Estudio de cohorte retrospectivo nacional para identificar los factores de riesgo de letalidad por hospitalización durante 30 días en casos de gripe confirmados por laboratorio.

OBJECTIVE: To identify factors associated with the risk of death in adolescent and adult inpatients with laboratory-positive (reverse-transcription polymerase chain reaction) influenza in Mexico during consecutive influenza seasons (2018-2020). PATIENTS AND METHODS: A retrospective cohort study used national surveillance system data, enrolling 3422 individuals. The association between various risk factors and 30-day in-hospital lethality were evaluated through risk ratios (RR) and 95% confidence intervals (CI). RESULTS: The lethality rate was 18.1%. Flu vaccination history (RR = 0.56, 95% CI 0.42-0.78), early antiviral drug administration (≤ two days from symptom onset [reference ≥ 5 days], RR = 0.68, 95% CI 0.58-0.81), and a history of asthma (RR = 0.66, 95% CI 0.47-0.95) showed protective effects against influenza-attributable death. Mechanical ventilator support produced the highest increase in death risk (RR = 3.31, 95% CI 2.89-3.79). Male sex, older age, AH1N1 subtype, and other chronic diseases were also associated with fatal in-hospital influenza-related outcomes. CONCLUSIONS: Our findings highlight the major relevance of promoting immunization in high-risk individuals, together with ensuring early and effective antiviral management in suspected influenza cases.

[Effect of influenza vaccination in Primary Healthcare workers and the general population in Gran Canaria: A cross-sectional study]. / Efecto de la vacunación antigripal en trabajadores de atención primaria y población general de Gran Canaria: estudio transversal.

OBJECTIVE: To estimate the effect of the influenza vaccination in Primary Healthcare workers and the general population vaccinated during the 2015/2016 campaign. DESIGN: Cross-sectional study. SETTING: All the Primary Healthcare centres within the Gran Canaria healthcare region. PARTICIPANTS: A total of 1,868 Primary Healthcare workers (33.5% men; 66.5% women) and 795,605 individuals from the general population (49.4% men; 50.6% women). PRINCIPAL MEASUREMENTS: The outcome variables in Primary Healthcare workers were: influenza cases reported to the Epidemiological Surveillance System, and the sick leave days due to illness. In the general population: reported flu cases and vaccination coverage in connection with the vaccination status of the healthcare professional. The magnitude of association between vaccination and morbidity was estimated applying logistic regression models. RESULTS: Although not statistically significant, healthcare professionals that were not vaccinated had 1.7-fold increase in the risk of having influenza than those vaccinated. In the general population the association was significant in the female population (OR: 1.3; 95%CI: 1.1-1.5). Population coverage was significantly higher when both the doctor and nurse were vaccinated (OR: 1.3; 95%CI: 1.3-1.3), and reported flu cases decreased when the nurse was vaccinated (OR: 0.9; 95%CI: 0.9-0.9). CONCLUSION: A possible protective effect of influenza vaccination was observed in the general population, as well as an influence of Primary Healthcare workers on the patients regarding this. Even so, the low coverages registered point to a need to implement measures that may lead to a more favourable attitude towards influenza vaccination.

Analytical performance of the Alere™ i Influenza A&B assay for the rapid detection of influenza viruses.

The analytical performance of the new Alere™ i Influenza A&B kit (AL-Flu) assay, based on isothermal nucleic acids amplification, was evaluated and compared with an antigen detection method, SD Bioline Influenza Virus Antigen Test (SDB), and an automated real-time RT-PCR, Simplexa™ Flu A/B & VRS Direct assay (SPX), for detection of influenza viruses. An "in-house" RT-PCR was used as the reference method. Sensitivity of AL-Flu, SDB, and SPX was 71.7%, 34.8%, and 100%, respectively. Specificity was 100% for all techniques. The turnaround time was 13min for AL-Flu, 15min for SDB, and 75min for SPX. The Alere™ i Influenza A&B assay is an optimal point-of-care assay for influenza diagnosis in clinical emergency settings, and is more sensitive and specific than antigen detection methods.

[Monitoring respiratory syncytial virus through the Spanish influenza surveillance system, 2006-2014]. / Vigilancia del virus respiratorio sincitial en el marco del Sistema de Vigilancia de la Gripe en España, 2006-2014.

INTRODUCTION: The aim of the study is to analyze the information on respiratory syncytial virus (RSV) obtained through the Spanish Influenza Surveillance System (SISS) and to study its usefulness as supplementary information for the characterization of influenza epidemics. METHODS: The temporal patterns of both RSV and influenza viruses were analyzed by patterns comparing the weekly viral detection rates from 2006 to 2014. RESULTS: In general, the RSV circulation was characterized by showing a peak between 52-1 weeks, and circulated from 2 to 8 weeks before/prior to influenza viruses. CONCLUSION: RSV information obtained from the SISS is useful for the characterization of influenza epidemics in Spain.

Influenza infection in the intensive care unit: Four years after the 2009 pandemic.

UNLABELLED: The role of influenza viruses in severe acute respiratory infection (SARI) in Intensive Care Units (ICU) remains unknown. The post-pandemic influenza A(H1N1)pdm09 period, in particular, has been poorly studied. OBJECTIVE: To identify influenza SARI patients in ICU, to assess the usefulness of the symptoms of influenza-like illness (ILI), and to compare the features of pandemic vs. post-pandemic influenza A(H1N1) pdm09 infection. METHODS: A prospective observational study with SARI patients admitted to ICU during the first three post-pandemic seasons. Patient demographics, characteristics and outcomes were recorded. An influenza epidemic period (IEP) was defined as >100 cases/100,000 inhabitants per week. RESULTS: One hundred sixty-three patients were diagnosed with SARI. ILI was present in 65 (39.9%) patients. Influenza infection was documented in 41 patients, 27 (41.5%) ILI patients, and 14 (14.3%) non-ILI patients, 27 of them during an IEP. Influenza A viruses were mainly responsible. Only five patients had influenza B virus infection, which were non-ILI during an IEP. SARI overall mortality was 22.1%, and 15% in influenza infection patients. Pandemic and post-pandemic influenza infection patients shared similar clinical features. CONCLUSIONS: During influenza epidemic periods, influenza infection screening should be considered in all SARI patients. Influenza SARI was mainly caused by subtype A(H1N1)pdm09 and A(H3N2) in post-pandemic seasons, and no differences were observed in ILI and mortality rate compared with a pandemic season.

[Influenza vaccination. Effectiveness of current vaccines and future challenges]. / Vacunación antigripal. Efectividad de las vacunas actuales y retos de futuro.

Seasonal influenza is an annual challenge for health-care systems, due to factors such as co-circulation of 2 influenza A subtypes jointly with 2 influenza B lineages; the antigenic drift of these virus, which eludes natural immunity, as well as immunity conferred by vaccination; together with influenza impact in terms of morbidity and mortality. Influenza vaccines have been available for more than 70 years and they have progressed in formulation, production and delivery route. Recommendations on vaccination are focused on those with a higher probability of severe disease, and have a progressively wider coverage, and classically based on inactivated vaccines, but with an increasing importance of attenuated live vaccines. More inactivated vaccines are becoming available, from adyuvanted and virosomal vaccines to intradermal delivery, cell-culture or quadrivalent. Overall vaccine effectiveness is about 65%, but varies depending on characteristics of vaccines, virus, population and the outcomes to be prevented, and ranges from less than 10% to almost 90%. Future challenges are formulations that confer more extensive and lasting protection, as well as increased vaccination coverage, especially in groups such as pregnant women and health-care professionals, as well as being extended to paediatrics.

[Influenza vaccination coverage in children with risk conditions in Catalonia]. / Cobertura de vacunación antigripal en niños con condiciones de riesgo en Cataluña.

INTRODUCTION: Influenza vaccination is recommended in Catalonia in children older than 6 months with risk conditions for developing flu-related complications. The aim of this study is to determine influenza vaccine coverage in children with risk conditions and their association with socio-demographic factors and medical variables. MATERIAL AND METHOD: Descriptive cross-sectional study of children with risk conditions for developing influenza complications (aged between 6months and 15years old) assigned to Primary Health Care centers in Catalonia at the beginning of the 2011-2012 influenza vaccination campaign. The information on vaccination status and study variables were obtained from data registered on electronic health records by primary care teams. The relationship between influenza vaccination and demographic and medical variables was analyzed using bivariate analysis and a multiple logistic regression model. RESULTS: Influenza vaccination coverage was 23.9%. Variables associated with influenza vaccination were: age 2years or older (aOR: 1.6 [1.4-1.7] in children 3-5years old; 1.8 [1.7-2.0] in those 6-10 years, and 2.2 [2.0 -2.4] in children ≥11years]); male sex (aOR: 1.1 [1.0-1.1]); foreign nationality (aOR: 1.2 [1.2-1.3]); age-appropriate immunization according to the systematic immunization schedule (aOR: 3.3 [2.8-3.8]); more than one visit to the primary care physician (5 or more visits) (aOR: 4.1 [3.8-4.4]), and more than one risk condition (3 or more conditions) (aOR: 2.5 [1.6-3.9]). DISCUSSION: Compared to other countries, influenza vaccination coverage among children with risk conditions is low in our study. Strategies to improve coverage should be implemented.

Degree of adherence to recommended antiviral treatment during the pandemic and post-pandemic periods of influenza A(H1N1)pdm09 in 148 intensive care units in Spain.

OBJECTIVE: To determine the degree of antiviral treatment recommendations adherence and its impact to critical ill patients affected by influenza A(H1N1)pdm09 mortality. DESIGN: Secondary analysis of prospective study. SETTING: Intensive care (UCI). PATIENTS: Patients with influenza A(H1N1)pdm09 in the 2009 pandemic and 2010-11 post-Pandemic periods. VARIABLES: Adherence to recommendations was classified as: Total (AT); partial in doses (PD); partial in time (PT), and non-adherence (NA). Viral pneumonia, obesity and mechanical ventilation were considered severity criteria for the administration of high antiviral dose. The analysis was performed using t-test or «chi¼ square. Survival analysis was performed and adjusted by Cox regression analysis. RESULTS: A total of 1,058 patients, 661 (62.5%) included in the pandemic and 397 (37.5%) in post-pandemic period respectively. Global adherence was achieved in 41.6% (43.9% and 38.0%; P=.07 respectively). Severity criteria were similar in both periods (68.5% vs. 62.8%; P=.06). The AT was 54.7% in pandemic and 36.4% in post-pandemic period respectively (P<.01). The NA (19.7% vs. 11.3%; P<.05) and PT (20.8% vs. 9.9%, P<.01) was more frequent in the post-pandemic period. The mortality rate was higher in the post-pandemic period (30% vs. 21.8%, P<.001). APACHE II (HR=1.09) and hematologic disease (HR=2.2) were associated with a higher mortality and adherence (HR=0.47) was a protective factor. CONCLUSIONS: A low degree of adherence to the antiviral treatment was observed in both periods. Adherence to antiviral treatment recommendations was associated with lower mortality rates and should be recommended in critically ill patients with suspected influenza A(H1N1)pdm09.

Oxidative stress in immunocompetent patients with severe community-acquired pneumonia. A pilot study.

OBJECTIVE: A comparison was made of the oxidative stress (OS) levels of patients with either viral or bacterial severe community-acquired pneumonia (sCAP) and of patients without infection (healthy volunteers (HV) and patients with acute myocardial infarction (AMI)). DESIGN: A prospective observational study was made. PATIENTS: Critically ill patients with sCAP. VARIABLES: The TBARS level was measured as an index of oxidative injury. SOD, CAT and redox glutathione system (GSH, GSSG, GR, GPx) activities were measured as reflecting antioxidant capacity. Severity of illness was assessed by the APACHE II, SOFA and SIRS scores. RESULTS: Thirty-seven subjects were included: 15 patients with CAP (12 of bacterial origin [BCAP] and 3 due to 2009 A/H1N1 virus [VCAP]), 10 HV and 12 AMI patients. Intensive care CAP mortality was 26.7% (n=4). Plasmatic TBARS levels were higher in CAP patients than in HV, but similar to those recorded in AMI patients. In contrast, VCAP was associated with lower TBARS levels, and some components of the glutathione redox system were higher in BCAP patients and HV. The OS levels did not differ between survivors and non-survivors. CONCLUSION: Our results suggest the occurrence of higher OS in sCAP patients compared with HV. In contrast, lower TBARS levels were observed in VCAP patients, suggesting an increase of antioxidant activity related to the redox glutathione system. However, further research involving a larger cohort is needed in order to confirm these findings.

Effectiveness of influenza vaccine in preventing severe cases of influenza: Season 2022/2023.

INTRODUCTION: Influenza poses a significant burden in terms of morbidity and mortality, with vaccination being one of the most effective measures for its prevention. Therefore, the aim of this study is to determine the effectiveness of the influenza vaccine in preventing cases of severe influenza in patients admitted to a tertiary hospital during the 2022/23 season. METHODS: Case-control study. All hospitalised patients with a positive result in an RT-PCR for influenza were included. Those who met the criteria for a severe case (pneumonia, sepsis, multi-organ failure, admission to ICU or exitus) were considered cases. Those who did not meet these criteria were considered controls. Vaccine effectiveness (VE) to prevent severe cases and its 95% confidence interval were calculated. RESULTS: A total of 403 patients were admitted with confirmed influenza. Of these, 98 (24.3%) developed severe influenza. Of the total, 50.6% were men and 47.1% were over 65 years of age. VE adjusted for influenza type, age and certain comorbidities was 40.6% (-21.9 to 71.1). In a segmented analysis, influenza vaccine was effective in preventing severe cases in all categories. It was particularly relevant in the 65+ age group (VEa = 60.9%; -2.0 to 85.0) and in patients with influenza A (VEa = 56.7%; 1.5-80.9). CONCLUSION: Influenza vaccination markedly reduced the occurrence of severe cases of influenza in hospitalised patients, therefore, it remains the main strategy to reduce morbidity and mortality and associated costs.

Vaccination in pregnancy. Consensus document of the CAV-AEP and the SEGO.

During pregnancy, physiological changes in the immune response make pregnant women more susceptible to serious infection, increasing the risk for the mother as well as the foetus, newborn and infant. All women should be correctly and fully vaccinated as they enter their reproductive years, especially against diseases such as tetanus, hepatitis B, measles, rubella and varicella. In addition to the recommended vaccines, in risk situations, inactivated vaccines could be administered to women who were not correctly vaccinated before, while attenuated vaccines are contraindicated. Despite the fact that vaccination during pregnancy is a very important preventive measure and the existing recommendations from public health authorities, scientific societies and health professionals, the vaccination coverage could clearly be improved, especially against influenza and SARS-CoV-2, so any health professional involved in the care of pregnant women should proactively recommend these vaccines. The Spanish Association of Pediatrics (AEP), through its Advisory Committee on Vaccines, and the Spanish Society of Gynaecology and Obstetrics (SEGO) recommend vaccination against the following diseases during pregnancy: against influenza and COVID-19, in any trimester of pregnancy and during the postpartum period (up to 6 months post birth) in women not vaccinated during pregnancy; against pertussis, with the Tdap vaccine, between weeks 27 and 36 of gestation (in the CAV-AEP recommendations, preferably between weeks 27 and 28); and against RSV, with RSVPreF, between weeks 24 and 36 of gestation, preferably between weeks 32 and 36.

Respiratory syncytial virus infection in adults: Differences with influenza.

INTRODUCTION: Respiratory syncytial virus (RSV) causes an acute respiratory illness similar to influenza, although there are few data comparing both of them in adults. The existence of clinical differences between these two infections could have implications for their management. MATERIALS AND METHODS: Retrospective observational cohort study including 63 adults with positive PCR for RSV and 221 for influenza during winter 2018-2019. Epidemiological, clinical characteristics and outcomes were contrasted between both groups. RESULTS: Compared to influenza, RSV-positive patients presented a higher association with active neoplasia (OR=2.9; 95% CI: 1.2-6.9), dependence for basic activities of daily living (OR=3.4; 95% CI: 1.4-8.2) and immunosuppression due to chronic glucocorticoid administration (OR=7.6; 95% CI: 1.6-36.1). At diagnosis, fever was less common (OR=0.3; 95% CI: 0.2-0.7), and C-reactive protein level ≥100mg/l was more frequent (OR=2.1; 95% CI: 1.0-4.5). They developed bacterial co-infection by Staphylococcus aureus in a higher proportion (OR=8.3; 95% CI: 1.5-46.9) and presented a greater need for admission to the intensive care unit (OR=5.4; 95% CI: 1.4-19.2). CONCLUSION: RSV is an important cause of respiratory illness in adults during the influenza season. It especially affects vulnerable patients with chronic underlying diseases, and has a higher morbidity than influenza. For all these reasons, specific detection, prevention and treatment of RSV is necessary in order to reduce the consumption of health care resources due to RSV disease in adults.

Vaccination against seasonal flu in childhood and adolescence. Recommendations of the Advisory Committee on Vaccines and Immunizations of the Spanish Association of Pediatrics (CAV-AEP) for the 2024-2025 season.

The flu is a constant threat that can sometimes cause severe forms of disease. The highest incidence rates by age group occur in children under 15 years of age, especially in those under 5 years, in whom the rate of hospitalization is also similar to the population aged 65 years and older. In addition, children are the main transmitters of the infection. In Spain, 5 influenza vaccines are authorized for the paediatric age group: three inactivated tetravalent vaccines harvested from fertilised eggs, one tetravalent inactivated vaccine obtained from cell cultures and one attenuated tetravalent vaccine for intranasal administration, which will become trivalent in the 2024-2025 season by excluding the B Yamagata lineage as recommended by the WHO. The CAV-AEP recommends systematic vaccination in children aged 6-59 months, children and adolescents belonging to risk groups, people who can transmit the flu to groups at risk of complicated flu, and household contacts or close family of infants under 6 months. From 2 years of age, the intranasal attenuated vaccine is preferred due to its greater acceptability and thus contribution to greater vaccination coverage. The CAV-AEP also considers that vaccination against influenza of healthy children and adolescents aged 5-18 years is advisable, as it provides individual protection and promotes protection at the family and community levels. It is especially important to vaccinate all health care professionals against influenza as well as pregnant women at any time during pregnancy.

Executive summary. Management of influenza infection in solid-organ transplant recipients: consensus statement of the Group for the Study of Infection in Transplant Recipients (GESITRA) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI).

Solid organ transplant (SOT) recipients are at greater risk than the general population for complications and mortality from influenza infection. We have conducted a systematic review to assess the management and prevention of influenza infection in SOT recipients. Recommendations are provided about the procurement of organs from donors with influenza infection. We highlight the importance of the possibility of influenza infection in any SOT recipient presenting upper or lower respiratory symptoms, including pneumonia. The importance of early antiviral treatment of SOT recipients with suspected or confirmed influenza infection and the necessity of annual influenza vaccination are emphasized. The microbiological techniques for diagnosis of influenza infection are reviewed. Guidelines for the use of antiviral prophylaxis are provided. Recommendations for household contacts of SOT recipients with influenza infection and health care workers are also included. Antiviral dose adjustment guidelines are presented for cases of impaired renal function and for pediatric populations.

Management of influenza infection in solid-organ transplant recipients: consensus statement of the Group for the Study of Infection in Transplant Recipients (GESITRA) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI).

BACKGROUND: Solid organ transplant (SOT) recipients are at greater risk than the general population for complications and mortality from influenza infection. METHODS: Researchers and clinicians with experience in SOT infections have developed this consensus document in collaboration with several Spanish scientific societies and study networks related to transplant management. We conducted a systematic review to assess the management and prevention of influenza infection in SOT recipients. Evidence levels based on the available literature are given for each recommendation. This article was written in accordance with international recommendations on consensus statements and the recommendations of the Appraisal of Guidelines for Research and Evaluation II (AGREE II). RESULTS: Recommendations are provided on the procurement of organs from donors with suspected or confirmed influenza infection. We highlight the importance of the possibility of influenza infection in any SOT recipient presenting upper or lower respiratory symptoms, including pneumonia. The importance of early antiviral treatment of SOT recipients with suspected or confirmed influenza infection and the necessity of annual influenza vaccination are emphasized. The microbiological techniques for diagnosis of influenza infection are reviewed. Guidelines for the use of antiviral prophylaxis in inpatients and outpatients are provided. Recommendations for household contacts of SOT recipients with influenza infection and health care workers in close contact with transplant patients are also included. Finally antiviral dose adjustment guidelines are presented for cases of impaired renal function and for pediatric populations. CONCLUSIONS: The latest scientific information available regarding influenza infection in the context of SOT is incorporated into this document.

Impact and characteristics of hospital-acquired influenza over 10 seasons in a third-level university hospital.

OBJECTIVES: To analyze the characteristics of patients with nosocomial flu, to compare them with patients with community-acquired influenza to study possible differences and to identify possible risk factors associated with this type of flu. PATIENTS AND METHODS: Observational, cross-sectional and retrospective study of hospitalized patients with a microbiological confirmation of influenza in a third-level university hospital over 10 seasons, from 2009 to 2019. Nosocomial influenza was defined as that infection whose symptoms began 72h after hospital admission, and its incidence, characteristics and consequences were further analyzed. RESULTS: A total of 1260 hospitalized patients with a microbiological diagnosis of influenza were included, which 110 (8.7%) were nosocomial. Patients with hospital-acquired influenza were younger (71.74±16.03 years, P=0.044), had a longer hospital stay (24.25±20.25 days, P<0.001), had more frequently a history of chronic pulmonary pathologies (P=0.010), immunodeficiency (P<0.001), and were associated with greater development of bacterial superinfection (P<0.001), respiratory distress (P=0.003), and admission to the intensive care unit (ICU) (P<0.001). In the multivariate logistic regression analysis, the following characteristics were identified as independent risk factors: immunodeficiency (ORa=2.33; 95% CI: 1.47-3.60); ICU admission (ORa=4.29; 95% CI: 2.23-10.91); bacterial superinfection (ORa=1.64; 95% CI: 1.06-2.53) and respiratory distress (ORa=3.88; 95% CI: 1.23-12.23). CONCLUSIONS: Nosocomial influenza is more common in patients with a history of immunodeficiency. In addition, patients with hospital-acquired influenza had an increased risk of bacterial superinfection, admission to the ICU, and development of respiratory distress.

Old and new aspects of influenza. / Nuevos y viejos aspectos de la gripe.

Influenza is a classic infectious disease that, through the continuous variation of the viruses that produce it, imposes new challenges that we must solve as quickly as possible. The COVID-19 pandemic has substantially modified the behavior of influenza and other respiratory viruses, and in the coming years we will have to coexist with a new pathogen that will probably interact with existing pathogens in a way that we cannot yet glimpse. However, knowledge prior to the pandemic allows us to focus on the aspects that must be modified to make influenza an acceptable challenge for the future. In this review, emphasis is placed on the most relevant aspects of epidemiology, disease burden, diagnosis, and vaccine prevention, and how scientific and clinical trends in these aspects flow from the previously known to future challenges.

The new generation of messenger RNA (mRNA) vaccines against influenza.

Today there are multiple types of flu vaccines. The emergence of nucleic acid technology used in vaccines against SARS-CoV-2 suggests its future application against this infection. Against influenza, two types of vaccines have been developed based on messenger RNA (mRNA): conventional or non-replicative and self-amplifying or replicative (auRNA), both included in lipid nanoparticles. Animal studies carried out with the former have shown their strong capacity to induce Th-1 antibodies and cellular immunity against influenza haemagglutinin (HA) with few side effects. Human trials have shown 87% seroconversion and 100% seroprotection. The auRNA vaccines have obtained similar results in animals but at a concentration 64 times lower than the conventional one. Vaccines based on mRNA platforms meet the WHO requirements for next generation influenza vaccines.